Process for preparing pentamethylcyclopentaphosphine



States atent" 3,029,289 Patented Apr. 10, 1952 fiice The presentinvention relates to a novel process for the preparation ofcyclopentaphosphine. More particularly, it relates to the preparation ofpentamethylcyclopentaphosphine.

It is known that methyldifiuorophosphine can be converted to aS-membered heterocyclic phosphorous compound. The conversion takes placeeither upon heating or storing such methyldifluorophosphine.Unfortunately, however, the method for conversion of the particularalkyldifluorophosphine is not wholly satisfactory. In order to obtainthe desired conversion, only certain alkyldihalophosphines can beso-employed. It has been found that methyldifluorophosphine is the solereactant capable of such conversion. Hence, the aforementioned processis a rather limited one. Heating the particular dihalophosphinederivative or storing the same for prolonged periods of time, moreover,will induce cyclization to form pentamethylcyclopentaphosphine but onlyin poor yields. This is attributed to the fact that there isconcomitantly obtained a substantial amount ofmethyltetrafluorophosphine as an undesired side product. Due to thelimitation of initial reactant selection and the attendant low yields ofpentamer, the over-all process has not been cornmercially attractive.The present invention has for its object the provision which obviatesthe hereinabove mentioned difficulties.

To this end, it has been found that any methyldihalophosphine canunexpectedly be converted to the correspending cyclopentamer. Thereactant, methyldihalophosphine, can include the fluoro, chloro, bromoor iodo radicals. Surprisingly, the reaction can be carried out in aconvenient manner by causing the particular methyldihalophosphine toreact with a reducing metal, whereby the corresponding cyclopentamer isobtained in good yield and purity, and usually in excess of at leastfifty percent (50%) based on the weight of that reactant. In the processof the instant invention, no alkylphosphinetetrahalide as an impurity isobtained.

According to the process of the instant invention, amethyldihalophosphine is subjected to the action of a reducing metal,such as magnesium, sodium, potassium or lithium. Conversion or reductionof a dihalophosphine is slowly carried out at a temperature ranging fromabout 80 C. to about +l C., and preferably from 40 C. to about 25 C.Reaction is terminated when the reducing metal has been completelyreacted and recovered in the form of the halide salt. Usually thisoccurs within about twenty to about thirty hours at atmosphericpressure.

Advantageously, a number of dihalophosphines may be employed forpurposes of ready conversion. These are:

Methyl difiuorophosphine, Methyl dichlorophosphine, Methyldibromophosphine, and Methyl diiodophosphine.

Methyl dichlorophosphine is preferred as the reactant, for the reasonthat it is more readily available and is storagestable for prolongedperiods.

In general, the reduction reaction is preferably conducted in an inertetheral solvent. Illustrative of such solvents are: ether, dioxane,tetrahydrofuran, dimethyl ether of diethylene glycol and equivalentsthereof.

.not to be taken as limitative thereof.

Equivalent amounts of reducing metal and a methyldihalophosphine arebrought into reactive combination. Where lesser amounts of themethyldihalophosphine are used, a maximum yield of resultantcyclopentamer is not obtained. Thus, in order to insure completeness ofreaction so as to obtain maximum yields, at least an equivalent amountof the reactant will be required.

The following illustrative examples will serve to more fully describethe instant invention. These, however, are Unless otherwise noted, theparts given are by weight.

EXAMPLE 1 Preparation of Pentamet/zylcycloperttaphosphine In aflat-bottom vessel equipped with an efiicient stirrer are placed 2.04parts of lithium ribbon in 30 parts of dry tetrahydrofuran under anitrogen atmosphere. To the flask are slowly added with stirring at 40C. 17 parts of methyldichlorophosphine. The mixture is brought up toroom temperature and stirred until all the metal has reacted. Solvent isthen removed and the liquid material boiling up to 200 C. at 1 mm. Hgpressure collected. The liquid so-collected is redistilled to yield 5.0parts or 74% of pentamethylcyclopentaphosphine, having a boiling pointof from 110 C. to 112 C. at about 1 mm. Hg pressure.

Analysis in percent: Calculated-C, 26.10; H, 6.59; P, 67.33. Found-C,26,37; H, 6.80; P, 67.30.

EXAMPLE 2 The procedure of Example 1 is repeated in every detail exceptthat the reducing agent, lithium, is omitted whereby conversion to thecyclopentaphosphine is attempted. None of the cyclopentaphosphinederivative is detected.

EXAMPLE 3 Example 1 above is repeated, except that the reducing agent isomitted and the phosphine reactant is heated to about 100 C. Conversionto the cyclo pentamer is not observed.

EXAMPLE 4 The procedure of Example 1 above is followed except that 30.3parts of methyldibromophosphine are substituted for themethyldichlorophosphine reactant. Penta methylcyclopentaphosphine yieldof 5.4 parts corresponding to 79 percent is obtained.

Similar high yields of pentamethylcyclopentaphosphine are obtained wheneither methyldifluorophosphine or methyldiiodophosphine is substitutedfor the methyldibromo reactant above.

Advantageously, the product obtained from the process of the presentinvention finds utility as a polymerization accelerator for epoxy-typemonomers. Thus, the polymerization of diglycidyl ether of isopropylidenediphenol can be easily accomplished.

I claim:

1. A process for preparing pentamethylcyclopentaphosphine whichcomprises: bringing into reactive combination at a temperature betweenabout 80 C. and C. in the presence of an inert solvent for each of thereactants substantially equivalent quantities of a methyldihalophosphineand a reducing metal selected from the group consisting of sodium,potassium, lithium and magnesium, causing the reaction to continue forat least about twenty hours, and recovering so-formedpentamethylcyclopentaphosphine in good yield and purity.

2. A process according to claim 1, in which the methyldihalophosphine ismethyldifiuorophosphine.

3. A process according to claim 1, in which the methyldihalophosphine ismethyldibromophosphine.

3 4 4. A process according to claim 1, in which the methyl- 6. A processaccording to claim 1, in which the inert dihalophosphine ismethyldiiodophosphine. solvent is tetfahydrofllffln.

7. A process according to claim 1, in which the methyl- 5. A processaccording to claim 1, in which the tem- I dihalophosphrne ismethyldrchlorophosphine.

perature for carrying out the reaction is maintained ac between about-40 C. and +25. C. No references cited.

1. A PROCESS FOR PREPARING PENTAMETHYLCYCLOPENTAPHOSPHINE WHICHCOMPRISES: BRINGING INTO REACTIVE COMBINATION AT A TEMPERATURE BETWEENABOUT -80*C, AND +100*C, IN THE PRESENCE OF AN INERT SOLVENT FOR EACH OFTHE REACTANTS SUBSTNTIALLY EQUIVALENT QUANTITIES OF AMETHYLDIHALOPHOSPHINE AND A REDUCING METAL SELECTED FROM THE GROUPCONSISTING OF SODIUM, POTASSIUM, LITHIUM AND MAGNESIUM, CAUSING THEREACTION TO CONTINUE FOR AT LEAST ABOUT TWENTY HOURS, AND RECOVERINGSO-FORMED PENTAMETHYLCYCLOPENTAPHOSPHINE IN GOOD YEILD AND PURITY.